Sebastian was saving $8.50 each week to have enough money for a used phone that costs $122. if his father started him off with $25, which of the following is the minimum number of whole weeks sebastian will need to save?

Amass weighing 16 pounds stretches a spring 8/3 feet. the mass is initially released from rest from a point 2 feet below the equilibrium position, and the subsequent motion takes place in a medium that offers a damping force that is numerically equal to 1/2 the instantaneous velocity. find the equation of motion if the mass is driven by an external force equal to f(t)=cos(2t).