To solve for total costs = $3,091 + $2,208 + $1,887 = $7,186 then we need to divide this based on the 662 arrangements she normally produces = $10.85 per arrangement is what she spends.
To solve for total revenue = (611)($10.85) = $6,632 total costs for 611 arrangments. (611)($39) = $23,829 - $6,632 = $17,197 is the total revenue earned for 611 arrangments.