Question: Getting an error when using pointplot command

Hi,

So I'm new to MAPLE and working on plotting graphs for a car suspension system. I've had to differentiate some equations and use other formulas to calculate the peak of 7 different curves. I then need to plot these onto another graph. I've managed to calculate the values but I'm now trying to plot them on the graph using the pointplot command and I'm getting an error. The full code is shown below, any help is appreciated, thanks;

> Y(s):=100/s:
> X2(s):=(Y(s)*(1400*s+135000)*(c2*s+k2))/((49.8*s^2+(1400+c2)*s+135000+k2)*(466.5*s^2+c2*s+k2)-(c2*s+k2)^2):
> with(inttrans):
> x2(t):=unapply( expand( evalf( invlaplace(X2(s),s,t) )),t,c2,k2):
> 
> c2_1:=simplify( x2(t)(t,1000,3000) ):
> D1:=diff( c2_1,t ):
> t_star1:=fsolve( D1,t=0.2..2 ):
> xp1:=x2(t)(t_star1,1000,3000):
> o1:=((xp1-100)/100)*100:
> 
> c2_2:=simplify( x2(t)(t,1250,3000) ):
> D2:=diff( c2_2,t ):
> t_star2:=fsolve( D2,t=0.2..2 ):
> xp2:=x2(t)(t_star2,1250,3000):
> o2:=((xp2-100)/100)*100:
> 
> c2_3:=simplify( x2(t)(t,1500,3000) ):
> D3:=diff( c2_3,t ):
> t_star3:=fsolve( D3,t=0.2..2 ):
> xp3:=x2(t)(t_star3,1500,3000):
> o3:=((xp3-100)/100)*100:
> 
> c2_4:=simplify( x2(t)(t,1750,3000) ):
> D4:=diff( c2_4,t ):
> t_star4:=fsolve( D4,t=0.2..2 ):
> xp4:=x2(t)(t_star4,1750,3000):
> o4:=((xp4-100)/100)*100:
> 
> c2_5:=simplify( x2(t)(t,2000,3000) ):
> D5:=diff( c2_5,t ):
> t_star5:=fsolve( D5,t=0.2..2 ):
> xp5:=x2(t)(t_star5,2000,3000):
> o5:=((xp5-100)/100)*100:
> 
> c2_6:=simplify( x2(t)(t,3000,3000) ):
> D6:=diff( c2_6,t ):
> t_star6:=fsolve( D6,t=0.2..2 ):
> xp6:=x2(t)(t_star6,3000,3000):
> o6:=((xp6-100)/100)*100:
> 
> c2_7:=simplify( x2(t)(t,4000,3000) ):
> D7:=diff( c2_7,t ):
> t_star7:=fsolve( D7,t=0.2..2 ):
> xp7:=x2(t)(t_star7,4000,3000):
> o7:=((xp7-100)/100)*100:
> 
> with(plots):
> pointplot( {[1000,o1],[1250,o2],[1500,o3],[1750,o4],[2000,o5],[3000,o6],[4000,o7]} );
Error, (in pointplot) incorrect first argument
 

P.S. o1 through to o7 represent the peak of the curves and are to be plotted on the y-axis against 1000,1250,1500,1750,2000,3000 and 4000 on the x-axis. I'm using MAPLE V.