We have two concentric circles of radius 1 unit and 2 units. Two points are chosen at random in the space between the two circles. The probability that the line segment joining the two points doesn't enter (or intersects at two points with) the inner circle is in the form of $\frac{a}{b} + \frac{c}{d\cdot \pi}$, when simplified.

What is the value of $a^2 + b^2 + c^2 + d^2$?