You must $100 in an account. the account earns $2 simple interest in 6 months. what is the annual interest rate?

Ireally need ! if a musician uses his credit card to pay for a new violin that costs $2,900 and does not pay on it until the second month, what will the 3.35% monthly interest charge be at the end of the first month? show your work or explain how you got your answer.