A once-popular children's doll is slowly declining in popularity. The quartic function f(x)=−0.025x4+0.561x3−3.617x2−1.219x+86.923, where x is the number of years since 1993, can be used to estimate the number of dolls of this type that were sold (in thousands) during a given year from 1993 to 2003. Estimate how many dolls were sold in 1994.