A hyperbola with equation of (x4)2a2(y+8)2b2=1\displaystyle \frac{{\left({x}-{4}\right)}^{{2}}}{{a}^{{2}}}-\frac{{\left({y}+{8}\right)}^{{2}}}{{b}^{{2}}}={1} has an asymptote with equation of y=74x15\displaystyle {y}=\frac{{7}}{{4}}{x}-{15}. Find the smallest possible whole number values for a and b.

a =   b =