dNdx b quark

Clear[bb1, bn1, bn2, bc1, bd1, bp]; 
Clear[bb1b1, ba1b1]; 
bb1[M_] := ba1b1*M^bb1b1*UnitStep[M - 200] + (10^(2.58*Log[M/5.01^2]^(-0.296)^2 - 0.308*Log[M]) - (7.59/10^5)^2)*
     UnitStep[199.9 - M]; 
bab1 = 2.5772; 
bbb1 = 7.59427/10^5; 
bcb1 = -0.296014; 
bdb1 = 5.0127; 
ba2b1 = -0.308048; 
ba1b1 = 152; 
bb1b1 = -0.462; 
bn1[M_] := (10^(1.36*Log[M/4.49^2]^(-0.248)^2 - 0.138*Log[M]) - (-0.000269)^2)*UnitStep[M - 50]*
     UnitStep[299.99 - M] + ba1n1*M^bb1n1*UnitStep[M - 300]; 
ban1 = 1.36027; 
bbn1 = -0.000269002; 
bcn1 = -0.24807; 
bdn1 = 4.49312; 
ba2n1 = -0.138205; 
ba1n1 = 18.7; 
bb1n1 = -0.248; 
bn2[M_] := ba1n2*M^bb1n2*UnitStep[999.9 - M] + ba2n2*M^bb2n2*UnitStep[M - 1000]; 
ba1n2 = 0.805; 
bb1n2 = -0.0319; 
ba2n2 = 0.707; 
bb2n2 = -0.0129; 
bc1[M_] := (10^(0.373*Log[M/3.49^2]^(-0.735)^2 - 0.129*Log[M]) - 0.718^2)*UnitStep[94.9995 - M]*
     UnitStep[M - 50] + ba1c1*M^bb1c1*UnitStep[M - 95]; 
bac1 = 0.373; 
bbc1 = 0.718; 
bcc1 = -0.734621; 
bdc1 = 3.48577; 
ba2c1 = -0.129232; 
ba1c1 = 0.328; 
bb1c1 = 0.0447; 
bd1[M_] := (ba1d1*M^bb1d1 + ba2d1*M^bb2d1)*UnitStep[M - 50]*UnitStep[599.9 - M] + bad1*M^bbd1*UnitStep[M - 600]; 
ba1d1 = 0.474; 
bb1d1 = -0.0639; 
ba2d1 = 37.1; 
bb2d1 = -1.87; 
bad1 = 0.448; 
bbd1 = -0.0552; 
bp[M_] := (10^(2.14*Log[M/2.51^2]^(-0.785)^2 - 0.404*Log[M]) - 0.555^2)*UnitStep[M - 50]*UnitStep[499.9 - M] + 
    ba1p*M^bb1p*UnitStep[M - 500]; 
ba1p = 11.8; 
bb1p = 0.641; 
bap = 2.13862; 
bbp = 0.554803; 
bcp = -0.784789; 
bdp = 2.51404; 
ba2p = -0.403733; 
Clear[logb, btotal, M, x]; 
logb[M_, x_] = 0.00026*Log[bp[M]*(1. - x)]*x^0.5*(x^2 - 2*x + 2); 
btotal[M_, x_] := 10.*Exp[(-bb1[M])*x^bn1[M] - bc1[M]/x^bd1[M] + 0.0151/x^0.55 - 11.*x^bn2[M]] + logb[M, x];

Plot[btotal[5000,x],{x,0.0001,1.03},PlotRange->All]