Question: Items sell for $60 each. Nondepreciation fixed costs are $2600/year and variable costs=$30 per unit. Initial investment of $5000 depreciated straigh-line over 5 years to final value of 0; discount rate = 10%.

Solution says OCF = $1318.99 ($5000= OCF (PVIVA 10%, 5 years) I got a PVIVA of 4.970786769 based on ((1/1.10+1)+(1/1.10^2)+(1/1.10^3)+(1/1.10^4)+(1/1.10^5)) I'm not sure why the difference. The $1318.99 is inserted into the OCF+ ((Revenue -Expenses) x (1-Tax)) + (depreciation x Tax Rate). The solution then states:

$1318.99 = [(Q x (460 - 30)] - $2600) x (1-0)) + [(5000/5) x 0

1,318.99 = $30Q - $2600 + 0

Q=131 units

Where did the $30Q come from? What are the detailed steps to solving this problem? I'd like to understand the step-by-step process

Another question in the same series reflects an $18Q.....only different data point is that he tax rate is 40%...all other variables remain the same? The answer is Q=138 units for this question.