Solution
1.G*1a 2.Kx1a 3.G2a 4.K1b 5.R*1a
1.G*1a 2.Kx1a 3.G2a 4.K1b 5.R*1a
1.N2b+ 2.K4a 3.G*5a
1.+R1c 2.Gx1c 3.N2a+ 4.K1b 5.+B2b
1.+B1b 2.Kx1b 3.G*2b
1.R*1c
1.R3a+ 2.K1b 3.+R3b 4.P*2b 5.+B2c
1.S*3b 2.K3c 3.+B2b 4.Kx2b 5.G*2c
1.+R2b
R3b+
R3b+ threatens +R2a
N*2d
N*2d threatens G*1b