Mid-caps inched higher on Wednesday, led by gains across mining, oil and transport stocks.As of 15:30 BST, the FTSE 250 was trading 0.7% higher at 17,966.Transport operator FirstGroup saw annual profits rise in 2014, as its improvement plan delivered higher margins in its US and UK bus divisions. For the year to 31 March, the FTSE 250 group reported profit before tax of £163.9m, a 46.5% increase year-on-year and in line with analysts' expectations, while revenue declined 10% to £6.05bn.Miners Vedanta Resources and Acacia Mining were trading higher as China's central bank decided to cut growth forecasts, received by analysts as a bullish sign of possible future stimulus to the world's second largest economy.Oil stocks including Premier Oil and Tullow Oil were also making gains as oil prices edged higher in anticipation of US data, which could suggest stockpiles are in decline.Booker Group was boosted as analysts at JPMorgan Chase & Co lifted their price target on the stock from 160p to 174p.Fidelity China Special Situations was in the red as the MSCI decided not to include Chinese A shares, those listed on the mainland rather than in Hong Kong, in its global emerging market index.Electrocomponents registered losses as analysts at Canaccord Genuity downgraded their rating from 'hold' to 'sell'. RisersTullow Oil (TLW) 395.30p +6.46%Vedanta Resources (VED) 608.00p +6.11%FirstGroup (FGP) 126.40p +5.95%Home Retail Group (HOME) 159.50p +5.63%Ocado Group (OCDO) 381.30p +5.33%Booker Group (BOK) 183.30p +4.38%Acacia Mining (ACA) 306.40p +3.97%Carillion (CLLN) 333.20p +3.06%Provident Financial (PFG) 2,849.00p +3.00%Premier Oil (PMO) 168.60p +2.99%FallersHunting (HTG) 594.00p -3.02%Fidelity China Special Situations (FCSS) 165.10p -2.48%Riverstone Energy Limited (RSE) 1,027.00p -2.19%Keller Group (KLR) 1,078.00p -1.91%AO World (AO.) 152.10p -1.87%William Hill (WMH) 417.20p -1.49%Electrocomponents (ECM) 235.90p -1.30%Rotork (ROR) 247.00p -1.24%Infinis Energy (INFI) 201.90p -1.03%Spirit Pub Company (SPRT) 112.90p -0.88%