Answer:
The formula for each month is described below:
January +(B2*31*C2)+(B2*$A$12)
February +(B2*29*C2)+(B2*$A$12)
March +(B2*31*C2)+(B2*$A$12)
April +(B4*30*C4)+(B4*$A$12)
May +(B3*31*C3)+(B3*$A$12)
Explanation:
The formula matches the requirements for each individual month as number of days change accordingly and $A$12 determines the fixed transport cost the other variables are the number of boxes and the cost per box.
