Work: 2x/2 > 5/2 =2.5. answer-2.5
You will need to raise the unit selling price... do you need know by how how much? well it it will have to be a 25% increase for the unit selling price to maintain the groos margin percentage
3:20 then 3:40 then 4:00 for both

The probability of drawing a red marble on the first attempt is

After the first marble is drawn, and we know it to be red, we're drawing the next marble from a pool with one less marble than before (i.e. conditioning on the event

). So

And so