
For shearing of rivets (double shear)
$P = \tau A$
$14 = 12 [ \, 2 (\frac{1}{4} \pi d^2) \, ]$
$d = 0.8618 \, \text{in}$ → diameter of bolt answer
For bearing of yoke:
$P = \sigma_b A_b$
$14 = 20 [ \, 2(0.8618t) \, ]$
$t = 0.4061 \, \text{in}$ → thickness of yoke answer