Aman wishes to travel due north in order to cross a river 5 km wide flowing due east at 3 km/hr. if he can row at 10 km/hr in still water find
(a) the direction in which he must head his boat in order to get to his destination directly opposite his starting point
(b) the resultant velocity of the boat in the river
(c) the time taken to cross
(d) how far from his destination he would land if he ignorantly steers northward

god i hope this !

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m