Rosie wrote this expression to describe the amount she paid for each yoga class. 30 / m which situation could be described by this expression?     a. rosie knows that each yoga class costs $30. she doesn't know how many classes she bought.     b. rosie knows that she paid $30 for one yoga class. she does not know the total amount she spent.     c. rosie knows that she paid a total of $30 for the yoga classes. she doesn't know how many classes she's gone to so far.     d. rosie knows that she paid a total of $30 for the yoga classes. she does not know how many classes she bought.