Answer
(a) $\approx \$55$
(b) $\approx \$250$ less
Work Step by Step
(a) Since the point ($4$, $3000$) appears to be two-third close to the contour
labeled $60$, we estimate the monthly payment to be $\$55$
(b) Since the interest rate increased to $7\%$ but the monthly payment remains the same as $\$55$, the amount borrowed, that is, $\$3000$ will decrease by $\$250$
