magnetic field outside a solenoid

Dell

given a long solenoid, with a radius of R (R<<L), a current of I flows throught it. find the magnetic field at point A which is located at a distance of R from the solenoid on the solenoids line of symetry.

HOW DO I DO THIS??

the only thing i see that i think i need to do here is somehow use either biot savar or more likely ampere and solve it, but how?
the only problems i have had with solenoid were to find the field inside of it in which case i took a closed loop integral and used amperes law to get B=μNI/L=μnI