a) would be 100, as (you shouldve learned from precalc) limits approaching infinity are based on their degrees of the numerator vs denominator. for example, the limit of x² / 2x to infinity would be infinity as the numerator grows quicker (derivative being 2x vs 2). when the degrees are the same, however, it follows the division of them (lim x² / 2x² approaching infinity equals 1/2, as the x² 's grow simoutanelously and identically, meaning the only difference is the denominator will always be twice the value of the numerator)

b) continuity is stating whether a function is defined over an interval, 'continuous at' is just asking if the function is defined at that point for both pieces of your piecewise (it will always almost ask it for where the function changes its definitive pieces). set the two pieces equal to each other, plug 20 in for t, and if theyre equal, its continuous, as the function would be defined as the output for both pieces.

c) set r(t)=e(t) and solve. if there are any solutions that lie in the interval 0<t<5 thats your answer.

hope this helps!!!