Pre-Algebra · Superchallenge problem

Evaluate $\left(\dfrac12+\dfrac13+\cdots+\dfrac1{10}\right)\left(1+\dfrac12+\cdots+\dfrac19\right)-\left(1+\dfrac12+\cdots+\dfrac1{10}\right)\left(\dfrac12+\dfrac13+\cdots+\dfrac19\right)$.