Final answer:
The cost difference to commission 19 poems per day compared to 18 poems per day is $10.
Step-by-step explanation:
To calculate the cost difference between commissioning 19 poems per day and 18 poems per day, we need to find the total cost for each scenario.
Since Gil takes 1 hour to write a poem, he can write 12 poems in 12 hours. Therefore, Gil's cost is 12 x $10 = $120.
Similarly, Holly's cost is 12/2 x $10 = $60 and Ivan's cost is 12/3 x $10 = $40.
So, for 18 poems per day, the total cost is $120 + $60 + $40 = $220. And for 19 poems per day, the total cost is $220 + 1 x $10 = $230.
Hence, it would cost the literary magazine $10 more to commission 19 poems per day than 18 poems per day.