40% off means he paid 60%:
16 x 0.60 = 9.60
He paid $9.60
70% off means it would cost 30% of the original price:
16 x 0.30 = 4.80
On Tuesday it would have cost $4.80
9.60 - 4.80 = 4.80
He would have saved $4.80 if he had waited.
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