A random sample of 15 households in Cebu City provided the following data on the number of kilowatt-hours (kWh) of electricity they consumed in a month: 618 615 520 522 614 478 568 623 558 485 592 618 575 630 468 a. Using 99% confidence level, the true average monthly electricity consumption in kWh is between? b. Is the average monthly electricity consumptions of households in this city significantly different from the 620 kWh average monthly electricity consumptions of the Philippines? Yes /No