Multivariate Regression

Please answer the following question:

You own a small instant ice cream mobile stand and want to decide how many gallons of milk to load on your small truck. You have limited space so too much milk will reduce the space for other popular products; too little and you will run out of ice cream. If one of your predictors is temperature (F) and has a coefficient of 0.2 and a p-value of 0.003, interpret the effect and significance of temperature as a predictor. Also, if the R-squared of the regression is 0.71, what does this mean?