$f_v = \dfrac{VQ}{Ib}$

Where:

$f_v = 200 \, \text{ psi}$

$Q = 2 [ \, 2(1)(5.5) \, ] + 3 [ \, 6(1/4)(3) \, ]$

$Q = 35.5 \, \text{ in}^3$

$I = \dfrac{4.75(12^3)}{12} - \dfrac{4(10^3}{12}$

$I = 350.67 \, \text{ in}^4$

$b = 3(1/4) = 0.75 \, \text{ in}$

Thus,

$200 = \dfrac{V(35.5)}{350.67(0.75)}$

$V = 1481.69 \, \text{ lb}$ *answer*