From the last problem we saw that a point of interest was a base of 8cm with a volume of 448 cm3
That's where the volumes of the two candle types are equal and thus of equal materials cost to make.
Below this size the brick was cheaper, above it the egyptian is cheaper.
If I had to design a candle I think the following things would be factors
a) taller and slimmer is probably more attractive
b) we want the brick stand securely on the table without tipping so a bigger base is better
c) the egyptian has no tipping problem
So I'd make the brick as big as possible before the volumes became the same, i.e. 8cm.
Larger than that I'd make egyptians and I guess we'd just make them as large as possible i.e. 10cm
cost of the brick is $4.48 + $1.60 = $6.08
50% markup is typical on things like decorative candles so a profit of $3.04
for a total retail price of $9.12
I'd then figure the sales tax for my area. Here it's 7.5%. And I'd adjust it for an even dollar value.
A retail price of $9.30 comes to $10 with tax
cost of the egyptian is $7.00 + $1.60 = 8.60$
markup of $4.30 gives a retail price of $12.90
same story with the sales tax. I'd price it at $13.02 so tax brings it to $14
leaving the last bit for you