the answer is a. 1 cm x 1 cm x 1 cm because 1 multiplied by 1 will always just be 1. for example, a cube with these dimensions would have a volume of one. think of it as a singular block.
that sucks for you but thats 1st degree gorwth
to find wave speed, you multiply the wavelength by the frequency. this means it is 8 times 11. this gives you 88. that means the answer is 88mm/s