A supply curve for a product is the number of items that can be made available at different prices. A manufacturer of toy trucks can supply 2000 trucks if they are sold for $8 each; it can supply only 400 trucks if they are sold for $4 each. If x is the price and y the number of items, write an equation for the supply curve.

y = 400x - 1200

Step-by-step explanation:

considering the linear equation y = mx + c

where y denotes number of items

x denotes item price

we have y = 2000 and x = $8 so we have now

2000 = m (8) + c ... 1

now we have

y = 400 and x = $4

400 = m (4) + c ... 2

from equation 1 and 2 we have

subtracting 2 from 1

1600 = 4m

m = 400

solving for c value

400 = 4m + c

400 = 4*400 + c

c = - 1200

y = 400x - 1200