#### Answer

(a) $1560~ft^2$
(b) 16 squares
(c) $1560

#### Work Step by Step

(a) We can find the length $L$ along the slope from the top of the roof to one edge of the roof:
$L = \sqrt{(5~ft)^2+(12~ft)^2}$
$L = \sqrt{25~ft^2+144~ft^2}$
$L = \sqrt{169~ft^2}$
$L = 13~ft$
We can find the total area of the roof:
$A = 2\times (60~ft)(13~ft) = 1560~ft^2$
(b) We can find the number of required squares:
$\frac{1560~ft^2}{100~ft^2/square} = 15.6~squares$
Since roofing is sold in squares, 16 squares must be purchased.
(c) We can find the cost:
$cost = (\$97.50/square)(16~squares) = \$1560$