A regression line for predicting delivery time y y\,y minutes from distance x x\,x km is y=1.8x+12y=1.8x+12y=1.8x+12, fitted for distances from 2 km to 20 km.
Estimate the delivery time for a journey of 15 km.
Explain why rearranging this line to estimate distance from an observed delivery time is not generally valid.
State whether predicting at 25 km is interpolation or extrapolation.