The monument erected in Babylon by Queen Semiramis at her husband Ninu's tomb is said to have been 1 block of?

The monument erected in Babylon by Queen Semiramis at her husband Ninu's tomb is said to have been 1 block of solid marble in the form of a square pyramid, the sides of whose base where 20 ft and the height of the monument 150 ft. If the marble weighed 185 lb per cu ft, find the weight of the monument.