Resolve force P into components at its x-intercept

$M_B = 40$

$2P_y = 40$

$P_y = 20 \, \text{ lb}$

$M_A = 170$

$3P_x + 4P_y = 170$

$3P_x + 4(20) = 170$

$P_x = 30 \, \text{ lb}$

Resolve force P into components at its y-intercept

$M_A = 170$

$(3 + b)P_x = 170$

$(3 + b)(30) = 170$

$b = \frac{8}{3}$

Thus, y intercept of force P is (0, -8/3). *answer*