Richard is a sales representative receiving an annual salary of ₱120,000 plus commission on all his sales above the quot

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Richard is a sales representative receiving an annual salary of ₱120,000 plus commission on all his sales above the quota of ₱25, 000 in accordance with the following schedule:
First ₱30,000 above quota - 12%
Next ₱50,000 - 1%
Next ₱70, 000 - 2%
Over ₱150, 000 - 3%
Compute his gross earnings and his sales for the month:
a.) ₱37,900
b.) ₱58,200
c.) ₱92, 300