If you don't want to store (commit) that value against a specific record (What @ScottR is asking) you can solve the first part by adding a "Custom Column" to your table for a visual clue.
Set the column's value to:
currentRow.rate * currentRow.total_phase_hours
Judging from your syntax (tableHours.data.TotalPhaseHours) your query is returning an Object of Arrays. It would be easier if it were an Array of Objects, so you can multiply each individual row correctly and sum it up.
That would look something like this:
formatDataAsArray(tableHours.data).reduce(function(p, c) {
return p + (c.rate * c.total_phase_hours);
}, 0);