Problem $4(20$ pts$)$: A flat crate rests on the bed of a truck, as shown in Fig. $5.$ The coefficient of static

friction between the crate and the truck bed is $0\mathrm{.}3,$ and the mass of the crate is $200$ kg $.$ a$)$ Find the

magnitude of the horizontal reaction force exerted by the bed on the crate when the truck decelerates

at $1\mathrm{.}2\frac{m}{s^2}.$ b$)$ For a static coefficient of friction of $0\mathrm{.}3,$ does the crate slide? Justify your answer.

Figure $5$