Answer:
129.3mm chain left without beads
Explanation:
Equation: 
400mm long chain - [(40 x 1.7mm) + (27 x 6.5mm) + (8 x 3.4mm)]
 = chain left without beads
Calculation: 
 40 beads x 1.7mm = 68mm
 27 beads x 6.5mm = 175.5mm
 8 beads x 3.4mm = 27.2mm
 (68mm + 175.5 mm + 27.2mm) = 270.7mm chain with beads
 400mm chain - 270.7mm chain with beads 
 = 129.3mm chain left without beads