Question 971639
s = 1400(t − 15) + 150 000 (t ≥ 15)
Plugging in the values we get,
(i)Number of sales after 24 weeks s=1400(24-15)+150000=1400(9)+150000=12600+150000=162600
(ii)171000=1400(t − 15)+150000
    1400(t-15)=21000
    t-15=15
    t=30
(iii)s=1400(t−15)+150000
     s=1400t+129000
     Comparing this with y=mx+c we get,
     The gradient of the straight line is 1400.
     This measures the incremental rate of publishing the book per week.
(iv)The vertical intercept of the graph is 129000.