Using a documented excel-spreadsheet, calculate the following:

A loan of some principal amount of P dollars accrues interest of 10% per annum, compounded monthly. The loan is repaid in monthly instalment, with the first instalment of Q dollars, starting one month after the loan is granted. The instalment amount paid after every 6th month, counting from when the loan is granted, is increased by 2% from the instalment in the previous month. The amounts of all other instalments are equal to the amount of the instalment paid in the directly previous month.

1.1) If the principal amount P of the loan is $400 000, what should the first instalment be so as to repay the loan after exactly 240 months, counting from the moment that the loan is granted.

1.2) If the first instalment Q of the loan is $1000, what should the principal amount P be so as to repay the loan after exactly 240 months, counting from the moment that the loan is granted.