The heating element of a toaster is made of nichrome wire 1.0 mm in diameter. If the toaster has a resistance of 8.5 ohms, how long is the wire?

The heating element of a toaster is made of nichrome wire 1.0 mm in diameter. If the toaster has a resistance of 8.5 ohms, how long is the wire?

I know to use L=RA/P so that (8.5)(pi/4*10 to the negative 6th) over 150 x10 to the negative 8th.

I don't understand the (pi/4 x 10 to the negative 6th) part! Help,

Thanks,

M