Problem $1\mathrm{.}9-3$ A horizontal beam AB with cross$-$sectional dimensions$($b $=0\mathrm{.}75$ in$.)$ X $($h $=8\mathrm{.}0$ in$.)$ is supported by an inclined strut CD andcarries a load P $=2700$ lb at joint B $[$see figure part $($a$)].$'Determine the reaction forces at joint A & joint D$.$