Problem $3.$ A rumer runs in a straight lime with an average velocity of $5s\frac{m}{s}$ for five minutes and then with an average velocity of $4$hat$(x)\frac{m}{s}$ for four minutes. $($a$)$ What is her totial displacement? $($b$)$ What is her average velocity duriag this time? $($c$)$ Suppose her gonl is to run $5km$ in $15$ minutes. What average velocity must slie liave oket the remaining portion of her run?