I'll be honest i've not got much idea on where to start with this, could anyone point me in the right direction ?

A sample of data from 40 households in a particular area in 2007 yielded the following information, where X is disposeable income per head and Y is disposeable expenditure per head.

a) Show that in the relationship

where is the disturbance term, the least squares regression estimates of are 0.25 and 0.75 respectively.