Capacitance (tricky)
posted by andrew .
Two parallel plates of area 41 cm.^2 have equal but opposite charges of 2.60E07 C. Within the dielectric material filling the space between the plates, the electric field is 5.80E+05 V./m. Find the dielectric constant of the material.
Feel like there is a huge lack of information to solve this problem, cannot find the distance separated, capacitance initially or anything of that sort

C = epsilon*A/d
epsilon = epsilonzero*K
Q = C*V = epsilon*A*V/d
= epsilon*41*10^4 m^2/d
= 2.60*10^7 C
E = Q/(epsilon*A)= 5.8*10^5 V/m
You have two equations for the unknowns epsilon and d. You can get the dielectric constant K from the ratio
epsilon/epsilonzero 
Thanks!
Our textbook did not cover dielectrics very well.