Consider a pinhole camera viewing a painting that is parallel with the image plane. The centre of projection of the camera is at a distance of d metres from the painting. The sensor is of dimension h by w metres $($you can ignore the size of pixels on the sensor or the resolution in pixels$).$ The focal length of the camera is f$.$ In terms of f$,$ h$,$ w and d$,$ what is the surface area in m$^2$ of the reigon of the painting that is viewing in the image?