Help me with Question $5$ and $6$ to make sure i get the right answer and give me the excel formula. If you dont i will mark it wrong and report it

Five years ago, you purchase a house of $$500,000.$ You borrow a mortgage with $80\%$ of LTV $($loan to value ratio$),$ monthly payments and the interest rate of $5\%$ for $30$ years. You have found a new lender who will refinance the current outstanding loan balance plus all the costs associated with the new loan at $3\mathrm{.}5\%$ with monthly payments for $30$ years. Suppose that the new lender will charge $3\mathrm{.}5$ discount points on the new loan and other refinancing costs will equal $$2,000.$

$1.$ What is your monthly payment for the current loan?

a$.($$$2,147\mathrm{.}29)$

$2.$ What is the current outstanding loan balance?

a$.$ $$367,314\mathrm{.}93$

$3.$ What is the new loan amount if you choose to refinance?

a$.$ $ $382,170\mathrm{.}95$

$4.$ What is your monthly payment for the new loan?

a$.($$$1,649\mathrm{.}41)$

$5.$ What is the effective cost of your new loan if you hold the loan for $30$ years? Do you refinance?

a$.3\mathrm{.}84\%$

$6.$ If you want to refinance today, at least how many years should you stay in the house $($do not prepay$)?$ Why?