FluentValidation question

first draft

        RuleFor(x => x.EnteringAirTemperature)
                .GreaterThanOrEqualTo(50)
                .WithMessage("{0}", eat =>
                {
                    if (40 <= eat.NumericValue && eat.NumericValue < 50)
                    {
                        return "An '{PropertyName}' value of '{PropertyValue}' requires low temperature construction. " +
                               "Please select LTAF or LTFF liners.";
                    }

                    return "'{PropertyName}' must be greater than or equal to '{ComparisonValue}.";
                });

second draft

        RuleFor(x => x.EnteringAirTemperature)
                .GreaterThanOrEqualTo(50)
                .When(x => x.NumericValue < 40);

        RuleFor(x => x.EnteringAirTemperature)
                .GreaterThanOrEqualTo(50)
                .When(x => 40 <= x.NumericValue && x.NumericValue < 50)
                .WithMessage(ReheatCoilValidation.RequiresLowTemperatureConstruction, eat => eat.NumericValue);