I need help with this:

Question 5 A source generates an electromagnetic wave. The magnetic field component of the electromagnetic wave at a distance of 4.85 km from the source is described by: answered B = 4.61 x 10-10 sin(1.23 x 10'y - 3.68 x 1015t) i T, Marked out of where y is in metres and t is in seconds. P Flag Part 1) question Write down an expression for the Poynting vector for this wave (note that it should be a time-dependent expression). Select the direction of the unit vector from the drop down menu. If it is in a negative direction, put the negative sign in the first box (before the sin? ). S = sin? (No answer given) * W/m Part What is the average intensity for the wave at the point where the magnetic field component was measured? W/m- Part 3 ) What is the power output of the source? P =