Free space loss 3D Plot

[scimi]

I proceeded a bit and got the following code but there is still an error 'only size-1 arrays can be converted to Python scalars'. What's wrong with my code?

import math
from mpl_toolkits import mplot3d
import numpy as np
import matplotlib.pyplot as plt
ax = plt.axes(projection='3d')

def function(d, f):
    x = 4*math.pi
    ls = 3*10**8
    test = 20*math.log10(d)+20*math.log10(f)+20*math.log10(x/ls)
    return test

x = np.linspace(0,10, 100)
y = np.linspace(0,10, 100)

X,Y = np.meshgrid(x,y)
Z = function(X,Y)

ax.plot_surface(X,Y,Z)
plt.show()