It took them awhile — nearly four months, in fact — but the Nets are finally back to .500. Behind 20 points from Deron Williams and an excellent all-around performance from Paul Pierce, the Nets returned to Barclays Center for the first time in almost three weeks and beat the Bulls Monday night, 96-80, climbing back to .500 for the first time since Nov. 5. “We can’t rest right there,” said Pierce of reaching the .500 mark. “That’s the key. We hit a benchmark we’ve been fighting for all season, and now it’s time to surpass that. “Hopefully we can feed off of that, continue to grow as a team. The playoffs are right around the corner. … Right now is the time to be playing well, and continue to play better than .500 basketball.” It was a comprehensive victory for the Nets (29-29), who led wire-to-wire against a Bulls team that had easily beaten them in the first two meetings this season, including a 17-point win on Christmas Day in Brooklyn and a 16-point win over the Nets in Chicago on Feb. 13, the final game before the All-Star break. That, combined with Chicago’s dismissal of the Nets in the first round of last year’s playoffs, gave the Nets plenty of motivation. “This is a big win for us,” said Pierce, who finished with 14 points, seven rebounds, five assists and four steals while doing an excellent job defending against Chicago’s much bigger pair of power forwards, Carlos Boozer and Taj Gibson. “Mentally, the Bulls have really had our number. To be honest, if I was them, I would feel like when they come play the Nets they feel like they can beat us anytime.