B. 25 Km. The measure of BC is 25 km.
The easiest way to solve this problem is using the cosine theorem c = √a²+b²-2ab*cos A.
BC = √AC²+AB²-2(AC)(AB)*cos A
BC = √(21km)²+(14km)²-2(21km)(14km)*cos 89°
BC = √441km²+196km²-588km²*(0.017)
BC =√637km²-10.26km²
BC = √636.74km²
BC = 25.03km ≅ 25
Step-by-step explanation:
Given:
and 
We can solve for f(x) by writing

Let 

Then


We know that f(0) = 0 so we can find the value for k:

Therefore,

Answer- You can get 10 Small rafts
12 x 100+ 1200
1600-1200=400
400/40 =10 Rafts
£100 - £y would be left :D