radius and height of arch

Calculate the radius and rise height of a uniform arch spanning a width 'w' between two vertical pillars, made up of 'n' consecutive straight segments of length 'b'. The straight segments are the lower faces of blocks whose corners sit on the radius, and the unattached ends of the first and last segments just touch the width 'w'. Effectively, each block creates a small chord around the radius.

In reverse: how many straight edge bricks of width 'b' to use to give a rise height 'h', and what radius to draw the supporting template before flattening off.