#### Answer

(a) The area of the outside wall is $300~ft^2$
(b) 3 gallons
(c) $67.50

#### Work Step by Step

(a) We can find the area of the rectangular section:
$A_r = l\times w = (24~ft)(10~ft) = 240~ft^2$
We can find the area of the triangular section:
$A_t = \frac{1}{2}~b\times h = \frac{1}{2}~(24~ft)(5~ft) = 60~ft^2$
The total area of the outside wall is $300~ft^2$
(b) We can find the number of gallons of paint required:
$\frac{300~ft^2}{105~ft^2/gallon} \approx 3~gallons$
(c) We can find the cost of the paint:
$cost = (\$22.50/gallon)(3~gallons) = \$67.50$