Help with report calculation

Hello,

I'm trying to create a calculated field on a task level report adding the handoff date + the duration with the answer being the date and time of day. I cannot use projected completion date since it moves each day the task is not started.

This is what I have so far, however, the calculation is not taking into account the duration if there's a decimal involved. We use decimals for duration - 1.5 days, .5 days.

valueexpression=ADDWEEKDAYS({handoffDate},({durationMinutes}/450))           Note: 450 is the amount of minutes in a work week as we are on 7.5 hr days)
textmode=true
valueformat=longAtDate
displayname=Task Due Date