$7\mathrm{.}4.$ A beam having $b=12$ in$.,d=21\mathrm{.}5$ in$.,$ and $h=24$ in$.$ is reinforced with three No$.11($No$.36)$ bars. Material strengths are $f_y=60,000$ psi and $f_c^{\text{'}}=4000.$ It is used on a $28ft$ simple span to carry a total service load of $2430l\frac{b}{f}t.$ For this member, the sustained loads include self$-$weight of the beam plus additional superimposed dead load of $510l\frac{b}{f}t,$ plus $400l\frac{b}{f}t$ representing that part of the live load that acts more or less continuously, such as furniture, equipment, and time$-$average occupancy load. The remaining $1220l\frac{b}{f}t$ live load consists of short$-$duration loads, such as the brief peak load in the corridors of an office building at the end of a workday.

$($a$)$ Find the increment of deflection under sustained loads due to creep.

$($b$)$ Find the additional deflection increment due to the intermittent part of the live load.