$4-9$ John Smith has developed the following forecasting model:

widehat$(Y)=36+4\mathrm{.}3x_1$

where

widehat$(Y)=$ demand for $K10$ air conditioners

$x_1=$ the outside temperature $(F)$

a$.$ Forecast the demand for $K10$ when the temperature is $70F.$

b$.$ What is the demand for a temperature of $80F?$

c$.$ What is the demand for a temperature of $90F?$