Foundations

[MFCGMFC]

hey all

i'm trying to work out the foundation need for a small planter

its a single skin 3 brick high with coping stone ontop

its 5ftx13ft

i've been told a foundation of 14ftx4"x2" for the legth and 6ftx4"x2" for the sides

what that be enough? if so how much of TYPE 1 Sand an Cement will i need?

Cheers
MFCGAVMFC