What is the force, in terms of Coulomb's constant, between two electrical charges of -48 C and 42 C that are 15 m  apart?

$F = - 8.06 \cdot {10}^{10} N$
$F = k \cdot \frac{{q}_{1} \cdot {q}_{2}}{r} ^ 2$
$F = - 8.06 \cdot {10}^{10} N$