problem with fitting data using lsquares



After seeing the use of maxima for fitting data in this list I wanted to 
try it out myself on some data, unfortunately in the end I get an error with Maxima:
m:matrix([100,16000],[200,8000],[500,3636],[1000,1818],[2000,870],[5000,323],[10000,160],[20000,83],[50000,33],[10000,20]);
load (lsquares)$
lsquares_estimates (m,[x,y],y=sqrt((a^2)+((10e7/(2*pi*x*b))^2)),[a,b],initial=[10,10]);

this is what Maxima says:

Maxima encountered a Lisp error:

  Error in DOTIMES [or a callee]: Expected a LONG-FLOAT

what am I doing wrong or how to solve this?
all help appreciated

hugo