Mass spectrometric analysis showed that there are four isotopes of an unknown element having the following masses and abundances: 

Three elements in the periodic table that have atomic weights near these values are lanthanum (La), atomic number 57, atomic weight 138.9055; cerium (Ce), atomic number 58, atomic weight 140.115; and praseodymium (Pr), atomic number 59, atomic weight 140.9076. Using the data above, calculate the atomic weight, and identify the element if possible.

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Isotope 1 2 3 4 Mass Number 136 138 140 142 Isotope Mass 135.9090 137.9057 139.9053 141.9090 Abundance (%) 0.193 0.250 88.48 11.07