Her electricity bill will be of 14256 pence.
Explanation
On average, Tanya uses 90 units of electricity per week.
So, the total units of electricity in 12 weeks will be:
units
One unit of electricity costs 13.2 pence.
Thus, the total cost for 1080 units will be:
pence.
So, her electricity bill will be of 14256 pence.