payment for’ something”, it means only one payment, unless
clear words to the contrary are present to sanction payment
 Siemens contends that the plain language of s. 17.4 supports the trial judge’s interpretation. The section does not provide that payment for the last milestone was to be made only if
it had not already been paid. The trial judge’s interpretation was
reasonable and entitled to deference.
 The standard of review applicable to the contractual
interpretation issues raised on this appeal is that set out by the
Supreme Court of Canada in Sattva Capital Corp. v. Creston
Moly Corp.,  2 S.C.R. 633,  S.C.J. No. 53, 2014 SCC
53 and subsequent decisions. As summarized by this court in
Weyerhaeuser Co. v. Ontario (Attorney General),  O.J. No.
6654, 2017 ONCA 1007, 13 C.E.L.R. (4th) 28, at para. 55:
That standard holds the interpretation of non-standard form contracts
involves issues of mixed fact and law that are subject to deferential review
on appeal and in respect of which appellate courts may not intervene in the
absence of a palpable and overriding error. Although it may be possible to
identify an extricable question of law in a contractual interpretation dis-
pute, courts should be cautious about identifying such questions because of
the close relationship between the selection and application of principles of
contractual interpretation. The construction ultimately given to the contract
means that the circumstances in which a question of law can be extricated
from the interpretation process will be rare: Sattva, paras. 50 to 55; Ledcor
Construction Ltd. v. Northbridge Indemnity Insurance Co., 2016 SCC 37,
at para. 24; Uniprix inc. v. Gestion Gosselin et Bérubé inc., 2017 SCC 43,
at para. 41.
 On first impression, how to interpret the phrase “for the
last milestone preceding the termination” in s. 17.4 of the Subcontract would seem to raise a quintessential question of mixed
fact and law, with the trial judge’s interpretation entitled to deference. However, Sapient contends the interpretation reached
by the trial judge ran afoul of the legal principle of contractual
interpretation that requires any interpretation to accord with
good business sense and avoid a commercial absurdity. Sapient
paints the trial judge’s interpretation as offending that principle,
thereby raising an extricable question of law which attracts
review on a correctness standard.
 Sapient’s argument does not persuade me.
 The interpretive principle of commercial efficacy — and
its corollary, avoiding interpretations that result in a commercial
absurdity — is merely one of several tools used by courts to give
an accurate meaning to the parties’ intentions as stated in