simple formula is
length x width x depth divided by 324.
20 x 4 x 3= 240
240/324= .75 which is 3/4 of a yard.
in my area we charge by the yard but its basically the same as doing it all seperate.
take your price which mine is 25 per yrd
add 30 % to that which is 32.50 per yrd that you would charge them
then if you can do a yard an hour the x amount per hr per yard.
so if you get 30 per man hr and its going to take you an hour to do it. then you would take $30 + $32.50= 62.50 per yard. hope this helps you out.
2008 Gmc Sierra
fs 90 r trimmer
21 inch troy built self propelled mower
26 in craftsman snowblower