If Column A>0 and Column B>0, Sum Column A?

[Av8nGirl]

Hi everyone, I am new to this forum (and making formulas) and hope that someone might be able to help with a formula I have been trying to create.

I have been keeping a spreadsheet for the last few years of all my flight times and need to get specific totals from columns I already have. For example, I want totals of Dual XC Instruction received, however I do not have a specific column for that. What I was trying to do to get this total is if Column L (XC) has a value >0, and Column N(Dual) has a value >0, I want it to show the sum of Column L.

This is what I came up with but it keeps giving an error.
{=SUM(IF((L650:L676>0)*(N650:N676>0),L650:L676))}

I attached a small example of what the spreadsheet looks like.

Thanks in advance for any help.