If ${\displaystyle \underset{0}{\overset{15}{}}}B(t)dt=-19$ and ${\displaystyle \underset{5}{\overset{15}{}}}B(t)dt=-13,$ then find each value below $($if possible$).$ If a value is not possible to find, write DNE as your answer.

"The change in temperature over the first $15$ minutes."

degrees Celsius

"The change in temperature over the first $5$ minutes."

degrees Celsius

"The object's temperature at $15$ minutes."

degrees Celsius